The theory of continental drifting was first introduced by a German
meteorologist and geophysicist named Alfred Wegener in 1915, when he published
his book, The Origin of Continents and Oceans.He argued that the continents of Earth were once joined together to form
one giant continent, or supercontinent, called Pangaea.As a result of the Moon’s tidal influence, Pangaea began to separate
into continents that moved westward to the positions where they are today.This conclusion and several of Wegener’s other findings were opposed
and discarded during the theory’s development and especially after his book
was translated into several different languages, including English.In order to make his conclusions viable, he had to gather enough evidence
(Tarbuck and Lutgens, 2002).

Even though the amount of evidence Wegener collected was exhaustive, he
still had one major obstacle that he could not overcome alone.He was unable to provide a believable mechanism explaining
how the continents moved.He could
only give evidence proving that the continents were once joined together at one
period in time.After his death in
1930, his theory of continental drifting would be laid aside for about 20 years.Through the study of paleomagnetism, scientists finally began to see the
relevance of Wegener’s findings.

In his
studies, he primarily noted the “jigsaw fit of the continents” on opposite
coastlines of the Atlantic Ocean.This
consideration was what first indicated to Wegener that the continents might have
originally been joined together.Even
though his observation was very unrefined, later developments in studying the
continental shelf by Sir Edward Bullard and his associates in the 1960’s
showed that the continents of South America and Africa fit together almost
perfectly at a 900-meter depth (Tarbuck and Lutgens, 2002).

Another area
of evidence that he gathered was that of fossil evidence.In his studies, “Wegener cited documented cases of several fossil
organisms that had been found on different landmasses but which could not have
crossed the vast oceans presently separating the continents” (Tarbuck and
Lutgens, 2002).One of his major
examples is the Mesosaurus, a reptile whose remains were only found in eastern
South America and southern Africa.Wegener
concluded that since this reptile’s fossils were not found in different, more
diverse areas, then the two continents surely were connected in the past.

But what was
the mechanism responsible for the movement of such large landmasses?Wegener attributed this to the “tidal attraction of the sun and the
moon.”He believed that this
attraction affected the earth as well as the ocean.Wegener relied on the fact that tidal movements caused friction within
the earth causing a deceleration of its rotational speed, therefore dragging the
crust westward.Perhaps the biggest
gap in Wegener’s argument was that of how the continents actually moved
despite all the evidence he used to prove they were once joined.Since “the tidal force acting on the crust is extremely small,” this
drifting mechanism was not considered, and “most geophysicists then turned
away from Wegener’s theory” (Takeuchi and others, 1970).One of Wegener’s major opponents was Harold Jeffreys, who
also believed in the contraction of the Earth.In answer to Wegener’s proposed drifting mechanisms, Jeffreys rightly
suggested that “tidal friction of the magnitude needed to displace the
continents would bring Earth’s rotation to a halt in a matter of a few
years” (Tarbuck and Rutgens, 2002).

Before the idea of continental drifting was accepted, a geologist named
Eduard Suess developed his theory of terrestrial contraction in the late
1800’s and early 1900’s.His
theory stated that mountain building occurred as a result of the Earth shrinking
in size, and, as a result, the Earth’s skin formed wrinkles just as a
“desiccating apple” to “accommodate the diminishing
surface area.”The wrinkles that form on the Earth’s surface are made into mountains.He believed that a continuous continental crust initially covered the
whole earth.As the earth
contracted, he explained, parts of the crust collapsed and became ocean.This process occurred over and over in a continuous cycle changing the
ocean to land and the land to ocean (Oreskes, 1999).

The study of paleomagnetism,
or fossil magnetism, revived interest in continental drift after a brief gap
after Alfred Wegener’s death in 1930 until the early 1950s.Iron-rich minerals that cool off after a lava flow are magnetized once
they reach a certain temperature.At
this point, they cool off pointing at the currently existing magnetic lines of
force.Unless the rock is moved,
these minerals will stay pointing in this position retaining its “original
alignment.”Now they record the
history of the magnetic poles, and they can also reveal the latitude in which
they were originally formed.S. K.
Runcorn and his associates unexpectedly discovered that the magnetic alignments
of the iron-rich minerals in lava flows of different ages varied greatly.This meant either one of two things: the magnetic poles migrated or the
continents drifted.Scientists have since come to the conclusion that “if the
magnetic poles remain stationary, their apparent movement is produced by the
drifting of the continents” (Tarbuck and Lutgens, 2002).Finally, many years after his death, other scientists finally began to
believe in Alfred Wegener’s unbelievable idea of continental drifting.